This invention relates generally to gas turbine engines and, more particularly, to methods and apparatus for regulating bearing loads within gas turbine engine bearing assemblies.
Gas turbine engines include a high pressure compressor, a combustor, and a high pressure turbine. The high pressure compressor includes a rotor, and a plurality of stages. The rotor is supported with a plurality of bearing assemblies that include an inner race, an outer race, and a plurality of rolling elements between the inner and outer races. Maintaining bearing loads within pre-defined limits during engine operation facilitates extending a useful life of the bearing assembly.
To regulate the bearing load, at least some known gas turbine engines use compressor bleed air. The bleed air is routed through delivery lines including orifice plate assemblies. The orifice plate assemblies are multi-piece assemblies and each orifice plate assembly includes a discretely sized opening that limits an amount of airflow through the orifice plate assembly and thus regulates a pressure/flow from the air sources.
During engine operation, when engine parameters indicate that bearing load is exceeding pre-defined limits, engine operation is stopped and the orifice plate assembly is replaced with a different orifice plate assembly that has a different sized opening. Because each orifice plate assembly is discretely sized, a large inventory of plates is often maintained. Because of the complexity of the multi-piece orifice plate assemblies, replacing the orifice plate assemblies is often a time-consuming and costly process.
In an exemplary embodiment, an orifice plate assembly for a gas turbine engine facilitates extending a useful life of bearing assemblies within the gas turbine engine. Each orifice plate assembly is coupled within the engine in flow communication with an engine air source, and each includes a first body portion and a second body portion. The first body portion includes a channel and a flow opening. The channel is sized to receive the second body portion, such that the second body portion may slide with respect to the first body portion. More specifically, the second body portion may be positioned to cover any portion or all of the first body portion flow opening.
During engine operation, when parameters measured indicate that bearing loads are approaching pre-defined limits, the orifice plate assembly may be adjusted after engine shutdown to regulate air pressure and flow to facilitate maintaining bearing loads within the limits. More specifically, to adjust the orifice plate assembly, the second body portion is loosened from the first body portion and is repositioned with respect to the first body portion. As the second body portion is repositioned, a cross-sectional flow area through the first body portion flow opening is changed. When bearing loads are reestablished within the pre-defined limits, the second body portion is re-secured to the first body portion. As a result, the orifice plate assembly facilitates extending a useful life of a bearing assembly in a highly reliable and cost-effective manner.